Industry Minister Arthur Sinodinos disclosed the subscription three days before being contacted by the ABC.

The pay TV lobby group ASTRA offers the freebie to all federal parliamentarians for their electorate offices.

Many politicians have accepted and disclosed the subscription, while others, like Communications Minister Mitch Fifield, declined and paid for it themselves to avoid any potential conflict of interest.

But there is confusion about whether politicians need to declare the gift, with some raising concerns about "a grey area" in the rules.

Senator Hinch said he did not know the subscription was free and updated his interests within hours of being contacted by the ABC.

"I just presumed it was part of the parliamentary package," he said.

Senator Hinch called on all parliamentarians with Foxtel subscriptions to declare them, if they haven't already.

"Ignorance, we know with the dual citizenship, is not a defence," he said.

But fellow crossbench senator David Leyonhjelm, who also received a subscription, said he didn't think it was worth disclosing.

"The subscription was offered to all sitting MPs, therefore it is not mandatory to include it on the pecuniary interest register," he said.

A spokesman for the Treasurer said the subscription had been previously listed on his register of interests as "ongoing".